1. Field of the Invention
This invention relates to data storage systems, and more particularly, to a system wherein optical pulses are used to effect reversal of the optical domains of a material which exhibits structural phase transition, the data being written and read optically.
2. Description of the Related Art
The reading and writing of digital information on a media generally has employed ferromagnetic media wherein the direction of magnetization of small magnetic domains encodes digital information. Similarly, in ferroelectric and other media, the direction of microscopic dipole domains can be used to encode digital information. In the case of optically-read magnetic storage media, the direction of magnetization effects the reflection of a polarized laser light beam, whereby the encoded digital information can be read. There is, however, no currently available mechanism for repeatedly writing on these media whereby the information may be written and rewritten at will employing light only.
A currently available method for writing optically on a magnetic storage media (read/write optical dish) requires a small spot of the medium to be heated with an optical pulse. These known devices rely in their operation on the realization that coercive strength (i.e., the ease with which the magnetic dipoles in the material align to an external magnetic field) is a function of temperature. The optical disk is operated in a magnetic field, and when a spot of the medium is heated, a magnetic dipole of the disk aligns itself along the applied field. When the material is subsequently cooled, the magnetic dipole is fixed in its direction and will not realign to the field. In this manner, the direction of magnetization (and the data bit stored) at that point on the storage medium is fixed until another pulse is applied to heat that spot of the material. Thus, the rate at which the information can be written on such a medium is restricted by the rate at which the heat generated in the medium during the writing process can be conducted away.
It is, therefore, an object of this invention to provide a system wherein digital data can be stored and read using optical means exclusively.
It is another object of this invention to provide a system wherein digital data can be stored and read without requiring the application of an external magnetic field.
It is also an object of this invention to provide a system wherein digital data can be stored and read repeatedly using optical means exclusively.
It is a further object of this invention to provide a system wherein digital data can be stored and read repeatedly without requiring preheating of the storage location.
It is additionally an object of this invention to provide a fully optical switching arrangement which performs at very high speeds.
It is yet a further object of this invention to provide an optical data storage system wherein the operating speed is not limited by the cooling rate of the storage medium.
It is also another object of this invention to provide a data storage system wherein the reading and writing of data is performed exclusively optically with a very short switching time and with direct coupling to a fast optical interconnection or transmission line.
It is yet an additional object of this invention to provide a fully optical data write/read system which is relatively inexpensive to produce.
It is still another object of this invention to provide a fully optical data write/read system which does not require nanofabrication techniques to be employed during manufacturing.
It is a yet further object of this invention to provide a fully optical data write/read system which is nonvolatile and does not depend upon the application of a continuous electrical power to retain the data.
It is also a further object of this invention to provide a fully optical data write/read system which employs storage media materials which can be produced using developed technologies.